If you are going to Akihabara, I suppose you'll go to the big Yodobashi store? There you can try out different headphones.
Going by your description, my tip is the Audio Technica ESW9. They look very nice:
You could always check them out. I think that you can find them for around 25.000 yen.
There is a really good headphone store in Akihabara. It might be a bit difficult to find, though.
I copy and paste my comment from another thread:
I suppose you have found your way to E-earphone in Akihabara? Of course Yodobashi is great, but they have even more headphones in the E-earphone store. http://gigaplus.makeshop.jp/gcom1420/ShopInfo/ShopInfoAkiba.html
I just love that place! They've got used headphones as well that you can get for a lower price. It is difficult to find the first time you go there. If you haven't been there before, exit the Chuo line station towards Electrictown and then cross the big road (Chuo dori). Follow it down away from the station until you pass a tall black building on your left side. Turn left and right into the first parallel street to Chuo dori and the E-earphone shop is opposite to a Sofmap store. The building is called Rock 2 building and E earphone is on the 5th floor.
Anyway, if you have already been there, the description is not necessary.
You should check the Audio Technica ES10 out as well, however they are a bit more expensive and do not isolate as well as the HD25. I bought mine at a Yodobashi store in Shinjuku October when I went to Japan. They cost 30.000 yen at Yodobashi. You can try out all three and compare.
Anyway, spend some time in the store comparing different headphones. And remember to get a Japanese brand. European and American brands are more expensive in Japan.
Edited by Danneq - 6/22/12 at 4:18pm